1. Field of the Invention
The present invention relates to a bonding method of electronic parts in which when a metal cap is fixed and sealed on a package substrate of an extremely small size of surface mounting type quartz oscillator or the like and an extremely small size of IC chip or the like is mounted on a substrate, a sealing condition or a mounting condition due to excellent bonding can be realized by utilizing ultrasonic coupling oscillation.
2. Description of the Prior Art
Presently, miniaturization and light weight manufacture for personal equipment such as mobile body communication apparatus such as a portable telephone, note type personal computers, digital VTR cameras or the like are remarkably progressed. In that trend, electronic parts integrated into such equipment is required to be a more miniaturized shape so as to fit into a high integrated packaging.
Specifically, as shown in a phenomenon in which with respect to main electronic parts such as quartz oscillators, generators, filters or the like, the volume of a package size became approximately one fifth during the past 2 to 3 years, a rapid high integration trend has progressed.
For example, with respect to a quartz oscillator, there is a process in which a quartz piece as an oscillator is placed and sealed in an atmosphere of inert gas in order to ensure a stable clock oscillation frequency. Conventionally, resin sealing, glass sealing, or electric resistance welded sealing or the like are generally executed. This way is similar to the cases of generators or filters.
For the aforementioned sealing process, mainly the electric resistance welded sealing is frequently used in a point of view of sealing airtightness and sealing strength. However, in a present situation in which package sizes have become smaller as described above, upon sealing of a package with a 3.0 mm square or smaller, if the electric resistance welded sealing is adopted, there is a problem in which a distance between electrodes for welding may not be taken enough physically and electronic parts may be thermally broken down while thermal shock is applied to the work by the heat generated at the time of welding or the like.
That is, in the sealing method by the conventional electric resistance welded sealing, roller electrodes with tapers are provided on a sealing cap, and pulsation welding is executed under a constant pressure condition so that bonding is executed by Joule heat generated in the bonding portion. Thus, there is a problem in which thermal shock is given on the package substrate and microcracks in the substrate may be generated. Further, when the sealing cap is small, the control of the heat generated becomes difficult, thereby causing problems in which the sealing cap is melted by the heat generated, and the manufacture of fine roller like electrodes is extremely difficult or the like. Thus, the method seems not to be appropriate for sealing of small-size electronic parts in these points of view.
With respect to mounting of electronic parts, it is a present condition that a conventional wire bonding method, or a flip chip method cannot keep up with. That is, the connecting pad size of a highly densely packaged semiconductor integrated circuit is approximately 100 .mu.m square or smaller, and the distance between pads adjacent to each other is approximately 20 or shorter. Thus, when a conventional method is employed for bonding each IC pad, the bonding portions adjacent to each other are mutually superimposed and bonded, thereby causing an inconvenience in which an independent bonding portion is not ensured. This is a primary factor that prevents a miniaturization and a light weight manufacture of electronic parts.
In bonding electronic parts described above, although utilizing ultrasonic oscillation has been known in the past, since ultrasonic oscillation imparted at the time of bonding in the prior art is a single direction oscillation and further pre-heating that requires the biggest attention has to be given to this type of bonding, there are problems in which an excellent bonding cannot be obtained and the device may be broken due to an excessive pre-heating depending on the size, material or the like of the bonding object or the like.